Photodetector based on heterostructure of two-dimensional WSe₂/In₂Se₃

Heterojunctions formed by two-dimensional (2D) layered semiconducting materials have been studied extensively in the past few years. These van der Waals (vdW) structures have shown great potential for future electronic and optoelectronic devices. However, the optoelectronic performance of these devices is limited by the indirect band gap of multilayer materials and low light absorption of single layer materials. Here, we fabricate photodetectors based on heterojunctions composed of n-type multilayer α-indium selenide (In₂Se₃) and p-type tungsten diselenide (WSe₂) for the first time. The direct band gap of multilayer α-In₂Se₃ and type-II band alignment of the WSe₂/In₂Se₃ heterojunction enable high optoelectronic performance of the devices at room temperature in the air. Without light illumination, the dark current is effectively suppressed to 10^-13 A under -1 V bias and a high rectification ratio of 7.37 × 10³ is observed. Upon laser illumination with a wavelength of 650 nm, the typical heterojunction device exhibits a photocurrent on/off ratio exceeding 1.24 × 10⁵, a maximum photo responsivity of 26 mA W^-1 and a short photoresponse time of 2.22 ms. Moreover, the heterojunction photodetectors show obvious light response in the wavelength range from 650 nm to 900 nm. The present 2D vdW heterojunctions composed of direct band gap multilayer materials show great potential for future optoelectronic devices.